Chain pipe wrench



June 18, 1957 T. PETERSEN CHAIN PIPE WRENCH Filed Oct. 10, '1955 INVENTOR. PM

United rates Patent CHAIN PIPE WRENCH Thorvald Petersen, Erie, Pa., assignor to Reed Manufacturing Company, Erie, Pa., a corporation of Pennsylvarna Application October 10, 1955, Serial No. 539,326

1 Claim. (CI. 81-68) This invention is a chain pipe wrench having a head with a convex toothed gripping jaw on its under side and with a plurality of spaced chain hooks on its upper side. In such a wrench, the tension developed in the chain as the pipe is gripped can act in the direction to lift the chain out of the hooks if the slack in the chain is excessive. Since the wrench .will grip even though the chain has excessive slack, this condition can occur inadvertently and lifting the chain out of the hooks under load can damage the hooks. This invention is intended to prevent such damage to the chain hooks by making it impossible to grip pipe whenever the slack in the chain is excessive. This result is accomplished by a blunt nongripping surface on the end of the jaw adjacent the hooks projecting outside the envelope of the teeth so as to keep the pipe out of contact with the teeth whenever the slack in the chain is excessive.

In the drawing, Pig. 1 is a side view of the pipe wrench, and Fig. 2 is a fragmentary top view of one of the chain hooks.

The invention is shown applied to the pipe Wrench described in greater detail in application, Serial No. 433,774, filed June 1, 1954, now Patent 2,726,564. As there disclosed, the pipe wrench has a handle 1 having at its front end a head 2 provided on its under side with a pipe jaw 3. At the front and back ends of the jaw 3 are convex or arcuate toothed gripping surfaces 4 and 4a centered respectively on points 5 and 5a. The envelopes of the convex toothed surfaces 4 and 4a are respectively indicated by the dotted lines 6 and 6a which are generally tangent to the ends of the head. The toothed gripping surfaces 4 and 4a are symmetrically arranged on the underside of the jaw 3, the teeth 4 being used for counterclockwise turning and the teeth 4a being used for clockwise turning.

At the back end of the head is a pin 7 which provides a fixed anchor for one end of a chain made up of links 8 connected by pins 9, each of which as shown in Fig. 2 has projecting ends 10. On the upper side of the front end of the head are a plurality of hooks 11 for receiving the projecting ends of the pins and adjustably anchoring the chain in position to grip the pipe. As shown in Fig. 2, the chain hooks are formed by a pair of spaced walls 12 integral with the head and defining a slot 13 therebetween for receiving the chain links. Each of the walls 12 has a series of aligned notches 14 having the same spacing or pitch as the pins 9 so that the pins easily fall into the notches. The notches 14 are spaced apart along a center line 15 which as shown in Fig. 1 is inclined downwardly toward the front of the head at an acute angle with the head.

The wrench can be used with a substantial variation in the amount of slack in the chain. While this is advantageous because it does not require precise adjustment of the length of the chain, there is a possibility that the wrench may be used with an excessive amount of slack in which case the tension developed in the chain will tend to lift the pins out of the notches 14 and round off the holding surfaces 16 of the notches so that the holding power of the notches will be destroyed. When the slack in the chain is no greater than the amount indicated in full lines in Fig. 1, the line of action of the tension in the chain is beneath the center line 15 so that the tension tends to hold the ends 10 of the pins against the bottoms of the notches 14. This is the position for most effective holding. The full line position in Fig. 1 indicates the maximum allowable slack in the chain. Ordinarily the chain will have less slack. When the slack in the chain is increased by an additional link as shown in dotted lines in Fig. 1, the line of action of the tension in the chain is above the center line 15 and would tend to lift the ends 10 of the pins out of the notches 14. This lifting action would take place after the tension had been developed and, accordingly, the holding surfaces of the notches would become rounded and the holding power decreased. This action is prevented by the blunt non-gripping projections 17 or '17a which project radially outside the envelopes 6 or 6a of the teeth 4 or 4a as the case may be and hold the teeth out of engagement with the pipe whenever the slack in the chain reaches the excessive amount indicated in dotted lines in Fig. 1. Accordingly, when the slack is excessive, the chain cannot be tightened and the user is warned by the slippage that the excessive slack must be removed before the wrench can be used. The problem of excessive slack in the chain is more acute in larger sizes of pipe. The height of the projections 17, 17a is accordingly designed to prevent gripping of the largest size pipe which can be handled with the wrench whenever excessive slack in the chain would bring the line of action of the tension in the chain above the center line 15. This automatically takes care of the smaller sizes of pipe which require lesser height :of the projections. The projections 17, 17a have the additional advantage of keeping the pipe nearer the center of the wrench which provides better stress distribution. It will be noted that the projection 17 is at the front end of the head or the end adjacent the notches 14.

What is claimed as new is:

'In a chain pipe wrench, a handle having at one end an offset head with a convex toothed gripping surface at the front of the head on its under side with the teeth having an arcuate envelope, a chain having pinned links with the ends of the pins projecting outside the links, means anchoring one end of the chain at the back of the head, a plurality of spaced chain hooks on the upper side of the front of the head, said hooks having walls spaced apart to receive the chain links therebetween and a plurality of pairs of aligned notches in said walls each receiving the projecting ends of one of the pins, the notches being spaced apart along a center line inclined downwardly toward the front of the head at an acute angle with the head, and a blunt non-gripping surface projecting radially outside the envelope of the toothed gripping surface at the front end of the head adjacent the notches for engaging the pipe and holding the teeth of said gripping surface out of engagement with the pipe whenever the chain links, while wrapped around the pipe, extend above said center line.

References Cited in the file of this patent UNITED STATES PATENTS 483,419 Brock 'Sept. 27, 1892 514,721 Mahnicke Feb. 13, 1894 1,410,993 'Carll Mar. 28, 1922 2,726,564 Petersen Dec. 13, 1955 FOREIGN PATENTS 202,141 Great Britain Aug. 16, 1923 

